The present invention relates in general to infiltration or extravasation detection apparatus and pertains, more particularly, to infiltration or extravasation detection employing microwave radiometer measurement detection. Using microwave radiometric detection, it is possible to measure sub-surface tissue temperatures and thus provide a more instantaneous response time.
Various liquids such as water, electrolytes, sugar, blood, and pharmaceuticals are commonly administered to hospitalized patients from a container using a needle, commonly referred to as an intravenous needle that is adapted to be inserted into a superficial vein or artery. Any movement by the patient or improper insertion of the intravenous needle causes the tip of the needle to pierce the vascular wall and this causes the liquid that is being administered to undesirably enter the perivascular tissues. When this happens, the liquid may cause discoloration, discomfort and possible destruction of the tissue.
Two prior art patents that show typical infiltration detection systems are U.S. Pat. Nos. 3,618,602 and 4,010,749 both to Robert F. Shaw. Such systems enable detection of liquid infiltration so that the infusion of the liquid can be terminated. However, in connection with the injection of certain toxic liquids, typically used in cancer treatment applications, it is necessary to have extremely early detection of infiltration or extravasation. With thermistor sensor type systems as disclosed in the aforementioned Shaw patents, the response time is simply too slow and is furthermore subject to false alarms due to the need for pressure contact with the surface of the skin. Accordingly, particularly for infusion of more toxic liquids, present techniques are inadequate and can cause serious damage to the patient if the infiltration of the toxic liquid is not detected very early.
Another technique that has been used previously includes a pressure detection technique. More particularly, this technique has attempted to measure the swelling (the pressure build-up) caused by the leaking fluid under the skin. However, this technique also turns out to be ineffective for at least two reasons. The swelling under the skin tended to be broader than a small bubble area. Secondly, there was a significant delay in detection with this technique and thus the response time was extremely poor.
Accordingly, it is an object of the present invention to provide an improved infiltration detection system or apparatus in which the response time of detection is substantially improved in comparison with existing systems.
Another object of the present invention is to provide an improved infiltration detection system employing microwave radiometric detection that provides sub-surface temperature readings that thus provide more accurate detection.
A further object of the present invention is to provide an improved infiltration detection system employing passive, non-invasive apparatus for sub-surface thermal sensing.